The present invention relates generally to fasteners for plastic bags that are opened and closed by a slider, and, more particularly, to leak resistant fasteners.
Plastic bags are a popular household item used for a variety of uses such as storage of food. The addition of reclosable fasteners or zippers to these bags has further enhanced their utility and the addition of a slider has made the fasteners easier to open and close.
Although sliders have made opening and closing the fasteners easier, some of the slider operated fasteners have leakage across the fastener when the fastener is closed. This is caused by a separation member or finger on the slider that extends between sides of the fastener. Even when the fastener is completely closed, a portion of the separation member extends into the fastener preventing closure of the fastener at that location. One solution to this leakage has been to remove a portion of a fastener track at the location of the slider in the fastener closed position. When the slider is in this location, the separation member is in this portion of the fastener track and the fastener is completely closed. Precise sizing and locating the removed portion is difficult and failure to remove the correct amount and in the correct location can result in leaking and possible operation failure of the slider.
Another solution to the problem of leakage is a slider with a pivoting separation member. When the slider is moved to close the fastener, the separation member pivots out of the fastener. When the slider is reversed to open the fastener, the separation member pivots down into the fastener. An example of this slider is disclosed in U.S. Pat. No. 5,871,281. These sliders are complex to design and manufacture and are costly. In addition, the fact that the separation member must pivot to operate impacts the reliability of the slider. There is a need for a low cost, highly reliable slider and reclosable fastener arrangement that is leak resistant.
The present invention is directed to a slider that when used to open and close a fastener on a plastic bag provides a leak resistant closure. The slider has a top, depending side walls, a front or nose portion with a ramp on the nose portion, a rear portion, and a separation member or finger formed on the underside of the top extending from the nose portion toward the rear portion. The ramp can instead be incorporated into the shape of the separation member. The leak resistant feature is accomplished by withdrawing the operable portion of the separation member from cooperating features of the fastener. The separation member has a wide portion and a narrow portion. The fastener includes a pair of tracks and each track has an interlocking profile. Each track has two ends with a termination on each end. As the slider closes the fastener, the wide and narrow portions of the separation member move within the fastener with the wide portion holding the profiles open. As the slider is moved to close the fastener, the fastener passes along the separation member from the wide portion to the narrow portion and this along with body of the slider moves the profiles together interlocking the profiles. This action is reversed during the fastener opening movement of the slider. One example of this opening and closing is described in U.S. Pat. No. 5,007,143 which is incorporated by reference herein. When the slider reaches the termination at the end of the fastener, the ramp on the slider engages and travels up the termination. As this occurs, the slider is pivoted up which moves the wide portion of the separation member out of from between the fastener allowing the profiles to interlock up to the termination. The shape and positioning of the ramping surfaces and the relative location of slider retention shoulders control the change in orientation of the slider and the stiffness of the fastener is also a factor. The ramp can include a lock such as an indention which snap locks onto the termination and reduces the likelihood of the slider accidently being moved to open the fastener enough to allow leakage.